Rapid, facile synthesis of conjugated polymer zwitterions in ionic liquids

Page, Zachariah A.; Liu, Feng; Russell, Thomas P.; Emrick, Todd

doi:10.1039/c4sc00475b

Cited by 20 publications

(20 citation statements)

References 47 publications

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“…Important among reaction conditions was the selection of base, noting that potassium carbonate led to degradation of the iso ‐indgo materials, probably a result of hydrolysis that affords brominated isatin and oxindole derivatives . Tetra‐ n ‐butylammonium fluoride (TBAF) was found effective as an alternative, providing enhanced solubility of the reaction mixture compared with the aqueous and ionic liquid conditions we described previously . The enhanced solubility in TBAF solution led to rapid coupling and higher molecular weights (≈20 kDa DPP polymers obtained using TBAF; ≈5 kDa using K 2 CO 3 ).…”

Section: Resultsmentioning

confidence: 99%

“…Conjugated polymer zwitterions (CPZs) differ from CPEs in that their pendent chains possess no net charge nor transient counterion, yet maintain a polar, hydrophilic character inherent to the zwitterion. CPZs have been incorporated into optoelectronic devices, including thiophene‐based CPZs as cathode‐modification layers in OPVs . CPZs generate large Δ values, as measured by ultraviolet photoelectron spectroscopy (UPS); on high work function metals like Ag, CPZs provide several‐fold improvement of PCE values .…”

Section: Introductionmentioning

confidence: 99%

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Tuning the energy gap of conjugated polymer zwitterions for efficient interlayers and solar cells

Page

Liu

Russell

et al. 2014

J. Polym. Sci. Part A: Polym. Chem.

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Narrow band gap conjugated polymer zwitterions (CPZs) were synthesized by Suzuki polymerization and characterized to understand their electronic properties and utility as cathode modification layers in solar cells. The polymers were prepared from diketopyrrolopyrrole (DPP) and iso‐indigo monomers containing sulfobetaine (SB) pendant groups, benefiting from an ion‐rich aqueous phase in the polymerizations. UV–vis absorption spectroscopy revealed the optical energy gap value for the CPZs, ranging from 1.7 to 1.2 eV. Ultraviolet photoelectron spectroscopy of the CPZs as thin layers on Ag metal showed that the pendent zwitterions impart an interfacial dipole (Δ) to the metal and a work function reduction of ∼0.9 eV. OPVs fabricated using a conventional bulk heterojunction (BHJ) device architecture of ITO/PEDOT:PSS/(PTB7:PC71BM)/CPZ/Ag led to dramatic improvements in power conversion efficiency (PCE) values relative to devices having bare Ag cathodes (PCE < 2% for bare Ag vs. 6.7–7.7% for CPZ/Ag). The benzothiadiazole (BT)/DPP polymer denoted as PT2BTDPPSB gave an optimal PCE of 7.7% in a conventional BHJ OPV device architecture fabricated on a Ag cathode. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 327–336

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tuning the energy gap of conjugated polymer zwitterions for efficient interlayers and solar cells

Page

Liu

Russell

et al. 2014

J. Polym. Sci. Part A: Polym. Chem.

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“…Acyclic diene metathesis polymerization of undecadienes and Suzuki coupling polymerization of zwitterionic thiophene monomers have also been performed in RTILs. (112,113).…”

Section: Transition-metal Catalyzed Polymerizationmentioning

confidence: 98%

Polymerization in Ionic Liquids

Zhang

Behera

Hong

et al. 2015

Encyclopedia of Polymer Science and Technology

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Room temperature ionic liquids (RTILs) have proved over recent years to be useful and unique reaction media for a variety of chemical reactions. Faster reaction rates and better selectivities are often observed in RTILs as compared to those in common organic solvents. In addition to these advantages, the low volatility, nonflammability, and recycling potential also help RTILs become a preferred alternative reaction medium to meet environmental and other requirements. This is evidenced by the ever increasing number of papers published in this area every year and interesting and important discoveries. When conventional free radical polymerizations are carried out in RTILs, there is an increase in the propagation rate due to the high polarity of the RTIL and a decrease in the termination rate because of the high viscosity of the RTILs, and thus the overall reaction rate is greatly increased along with an increase in molecular weight. For living/controlled polymerization such as atom transfer radical polymerization and radical addition‐fragmentation and transfer, the reactions in RTILs are still controllable with faster reaction rates and easy separation of catalysts and/or ligands from the resulting polymers. Nearly all types of polymerization processes have now been successfully conducted in RTILs, often with advantageous effects.

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“…Theinterfacial dipole increases the anode-cathode work function offset (F AÀC ), thus enhancing open circuit voltage (V OC ). [22] Polar semiconducting polymers,such as conjugated polyelectrolytes (CPEs) [23][24][25] and conjugated polymer zwitterions (CPZs), [26][27][28][29] provide large negative D values to metals,w ith an inherent tunability of electronic properties.W ed esigned novel CPZs as neutral, electronically active,h ydrophilic semiconducting polymers,having two pendant sulfobetaine groups per repeat unit. Such polymers promise to overcome the general shortcoming in most cathode modification layers (i.e., having aliphatic or p-type backbones) of inefficient electron transport that requires interlayers to be very thin (about 5nmo r less).…”

Section: Polymersolarcells(pscs)provideanavenuetoinexpensivementioning

confidence: 99%

Finely Tuned Polymer Interlayers Enhance Solar Cell Efficiency

et al. 2015

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Three conjugated polymer zwitterions (CPZs), containing thiophene-, diketopyrrolopyrrole-(DPP), and naphthalene diimide (NDI) backbones,w ere synthesized with pendant zwitterions,s pecifically sulfobetaine groups.D iboronate-ester-functionalized bithiophene and benzothiadiazole monomers were copolymerized with zwitterion-substituted dibromothiophene,D PP,a nd NDI monomers by A 2 + B 2 Suzuki polymerization. The CPZs were incorporated into polymer solar cells (PSCs) as interlayers between the photoactive layer and Ag cathode.The thiophene-based CPZs gave power conversion efficiencies (PCEs) of about 5%,w hile the narrow-energy-gap DPP-and NDI-based CPZs performed exceptionally well, giving PCEs of 9.49 %a nd 10.19 %, respectively.T he interlayer thickness had only am inor impact on the device performance for the DPP-and NDI-CPZs,afinding attributed to their electron-transport properties.U ltraviolet photoelectron and reflectance spectroscopies, combined with external quantum efficiency measurements, provided structure-property relationships that lend insight into the function of CPZ interlayers in PSCs.N DI-based CPZ interlayers provides ome of the best performing organic solar cells reported to date,a nd prove useful in conjunction with high-performing polymer-active layers and stable,h igh-workfunction, metal cathodes.

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Rapid, facile synthesis of conjugated polymer zwitterions in ionic liquids

Abstract: Ionic liquids (ILs) were utilized for the rapid air-stable Suzuki polymerization of polar zwitterionic thiophene monomers, precluding the need for volatile organic solvents, phosphine ligands and phase transfer catalysts typically used in conjugated polymer synthesis.

Cited by 20 publications

References 47 publications

Tuning the energy gap of conjugated polymer zwitterions for efficient interlayers and solar cells

Tuning the energy gap of conjugated polymer zwitterions for efficient interlayers and solar cells

Polymerization in Ionic Liquids

Finely Tuned Polymer Interlayers Enhance Solar Cell Efficiency

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